U.S. patent number 6,520,274 [Application Number 09/558,024] was granted by the patent office on 2003-02-18 for modular electric steering gear assembly.
This patent grant is currently assigned to Visteon Global Technologies, Inc.. Invention is credited to Ian Yiying Hwa, Edward Francis McElmeel, Jr..
United States Patent |
6,520,274 |
McElmeel, Jr. , et
al. |
February 18, 2003 |
Modular electric steering gear assembly
Abstract
A modular pinion gear housing subassembly and method for making
same, wherein the modular concept allows for testing and
calibration of critical steering gear components prior to final
assembly onto a electrically assisted rack and pinion power
steering assembly, increases packaging efficiency, and increases
potential for commonality of parts between vehicle platforms. The
modular pinion gear housing subassembly comprises as its main
components a pinion shaft having an input portion and an output
portion, a pinion gear, a gear mechanically coupled to the pinion
shaft, and a torque sensor coupled to the pinion shaft. The modular
pinion gear housing subassembly is substantially contained within a
pinion housing, with the input portion and the pinion gear
extending from the housing and available to be coupled with other
power steering components.
Inventors: |
McElmeel, Jr.; Edward Francis
(Milan, MI), Hwa; Ian Yiying (West Bloomfield, MI) |
Assignee: |
Visteon Global Technologies,
Inc. (Dearborn, MI)
|
Family
ID: |
24227857 |
Appl.
No.: |
09/558,024 |
Filed: |
April 25, 2000 |
Current U.S.
Class: |
180/444;
180/443 |
Current CPC
Class: |
B62D
5/0403 (20130101); B62D 6/10 (20130101) |
Current International
Class: |
B62D
5/04 (20060101); B62D 005/04 () |
Field of
Search: |
;180/443,444 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dickson; Paul N.
Assistant Examiner: Lum; L.
Claims
What is claimed is:
1. A method of assembling a modular pinion gear housing subassembly
for use in an electrically assisted power steering system, the
method comprising: forming a pinion subassembly; forming a torque
sensor subassembly, said torque sensor subassembly comprising a
torque sensor; forming a pinion housing subassembly; pressing a
lower contact bearing into a threaded housing to form a bearing
housing subassembly; installing said pinion subassembly within said
pinion housing subassembly; installing said torque sensor
subassembly within said pinion housing subassembly; and installing
said bearing housing subassembly into a pinion housing of said
pinion housing subassembly.
2. The method according to claim 1 further comprising testing said
torque sensor prior to final assembly into the electrically
assisted power steering system.
3. The method according to claim 1 further comprising testing said
torque sensor and an electric motor of said pinion subassembly
prior to final assembly into the electrically assisted power
steering system.
4. The method according to claim 1, wherein forming a pinion
subassembly comprises: pressing a gear of an electric motor onto an
output portion of a pinion shaft; and pressing a torsion bar onto
said output portion of said pinion shaft.
5. The assembly of claim 1, wherein forming a torque sensor
subassembly comprises: installing a torsion bar o-ring; pressing a
torque sensor support needle bearing into an input portion of a
pinion shaft; pressing a lower sensor disk of an optical torque
sensor into said input portion; pressing an upper sensor disk onto
a shoulder of an output portion of said pinion shaft; sliding said
output portion over a torsion bar and into said input portion; and
drilling and pinning said output portion to said torsion bar.
6. The assembly of claim 1, wherein forming a pinion housing
subassembly comprises: installing a snap ring on a pinion housing;
pressing an upper angular contact bearing onto said pinion housing;
and pressing a sensor dust seal into said pinion housing.
7. A modular pinion gear housing subassembly for use in an
electrically assisted power steering system having a rack, the
assembly comprising: a pinion housing subassembly; a torque sensor
subassembly coupled within said pinion housing subassembly, said
torque sensor subassembly comprising a torque sensor, a torsion bar
o-ring, and a torque sensor support needle bearing; a pinion
subassembly coupled within said pinion housing subassembly; and a
bearing housing subassembly coupled within said pinion housing
subassembly, wherein said torque sensor is capable of being tested
prior to final assembly on the electrically assisted power steering
system.
8. The assembly of claim 7, wherein said pinion subassembly
comprises: a pinion shaft; an electric motor coupled to an output
portion of said pinion shaft; and a torsion bar coupled to said
output portion, wherein said electric motor is capable of being
tested prior to final assembly on the electrically assisted power
steering system.
9. A modular pinion gear housing subassembly for use in an
electrically assisted power steering system having a rack, the
assembly comprising: a pinion housing subassembly, wherein said
pinion housing subassembly comprises a pinion housing, a snap ring
coupled to said pinion housing, an upper angular contact bearing
pressed onto said pinion housing, and a sensor dust seal pressed
into said pinion housing; a torque sensor subassembly coupled
within said pinion housing subassembly, said torque sensor
subassembly comprising a torque sensor; a pinion subassembly
coupled within said pinion housing subassembly; and, a bearing
housing subassembly coupled within said pinion housing subassembly,
wherein said torque sensor is capable of being tested prior to
final assembly on the electrically assisted power steering
system.
10. A modular pinion gear housing subassembly for use in an
electrically assisted power steering system having a rack, the
assembly comprising: a pinion housing subassembly; a torque sensor
subassembly coupled within said pinion housing subassembly, said
torque sensor subassembly comprising a torque sensor; a pinion
subassembly coupled within said pinion housing subassembly; and a
bearing housing subassembly coupled within said pinion housing
subassembly comprising a threaded housing and a lower angular
contact bearing pressed into said treaded housing, wherein said
torque sensor is capable of being tested prior to final assembly on
the electrically assisted power steering system.
11. A modular pinion gear housing subassembly for use in an
electrically assisted power steering system having a rack, the
assembly comprising: a pinion housing subassembly; a pinion shaft
subassembly coupled into said pinion housing subassembly; and a
threaded housing subassembly coupled into said pinion housing
subassembly, said threaded housing subassembly comprising a
magnetoelectric torque sensor comprising at least one torque
sensing coil, said threaded housing subassembly further comprising
a threaded housing, a snap ring coupled to said threaded housing,
and an upper angular contact bearing coupled to said threaded
housing; wherein said magnetoelectric torque sensor is capable of
being tested prior to final assembly on the electrically assisted
power steering system.
12. The assembly of claim 11, wherein said pinion shaft subassembly
comprises: a pinion shaft; an electric motor coupled to said pinion
shaft; a magnetoelectric sensor ring coupled to said pinion shaft;
and a snap ring coupled to said pinion shaft.
13. The assembly of claim 11, wherein said pinion housing
subassembly comprises: a lower control bearing; and a pinion
housing coupled to said lower control bearing.
Description
TECHNICAL FIELD
The present invention relates to the power steering systems and
more specifically to modular electric steering gear subassembly
design.
BACKGROUND
Over the years, power steering has become standard equipment on
most vehicles. Most late model passenger cars with power steering
use either a power rack and pinion system or an integral power
steering gear assembly. Most front wheel drive cars use power rack
and pinion systems, while most rear wheel drive systems use an
integral power steering gear. Power steering systems are typically
either hydraulic-based systems, where fluid pressure is used to aid
the steering assembly in turning a vehicle, or electric-based
systems, where an electric motor is coupled to the steering
assembly to aid the steering assembly in turning the vehicle.
Automobile power steering is actually power-assisted steering. All
systems are constructed so that the car can be steered manually
when the engine is not running or if the steering system is
disconnected from the power source.
One problem common to both hydraulic-based and electric-based power
steering systems is that the systems typically must be assembled
completely before they can be tested. If a problem in the initial
assembly is detected or if the overall system is not functioning
properly, the system must be disassembled to determine the root
cause of the problem and then be reassembled to test the replaced
component. This disassemble/reassemble process is time consuming
and costly.
Another problem with typical power steering assemblies is that they
are extremely bulky to ship when fully assembled. This bulkiness
increases costs associated with packaging efficiency.
Another problem with typical power steering assemblies is
commonality. Commonality is highly desirable in automotive assembly
plants or other industries, in that individual sub-assemblies may
be used on more than one platform. The more commonality among
parts, the more efficient the process to make vehicles, and the
more cost savings that can be achieved.
SUMMARY OF THE INVENTION
It would therefore be desirable to provide a modular power steering
assembly that is capable of being tested at various stages prior to
final assembly on a vehicle to ensure that various components are
functioning properly. It is also desirable that these assemblies
are capable of being shipped as subassembly components for
efficiency and cost reasons. The modular concept is also highly
desirable in that it increases the potential for commonality
between vehicle platforms.
The modular design concept has great advantages over typical power
steering assemblies. First, it allows the testing and calibration
of critical steering gear components independently prior to final
assembly.
Next, the modular design concept provides increased packaging
flexibility in two ways. First individual sub-assemblies may be
shipped independently of other components. Second, shipping costs
can be minimized by increasing the usable space in a container by
packaging the sub-assemblies prior to final assembly in a more
efficient and space conscious manner, not as a bulky final
assembly.
Third, the modular design concept can increase
component/subassembly commonality across vehicle platforms, which
can lead to tremendous cost savings.
Other objects and advantages of the present invention will become
apparent upon considering the following detailed description and
appended claims, and upon reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a electrically powered rack and
pinion power steering assembly having a pinion gear housing
subassembly according to a preferred embodiment of the present
invention;
FIG. 2 is a perspective view of a pinion gear housing subassembly
uncoupled from an electric motor according to a preferred
embodiment of the present invention;
FIG. 3 is a perspective view of the pinion gear housing subassembly
of FIG. 2;
FIG. 4 is a cross-sectional view of the pinion gear housing
subassembly of FIG. 3 taken through line 4--4;
FIG. 6 is a cross-sectional view where the pinion gear housing
subassembly is further assembled with an electric motor and a rack;
and
FIG. 7 is a cross-sectional perspective view another preferred
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring to FIG. 1, an electrically powered rack and pinion power
steering assembly 10 of a vehicle 11 having a modular pinion gear
housing subassembly 16 according to a preferred embodiment is
shown. The assembly 10 also has as its major components a steering
wheel 12 connected to a steering shaft 14 that cooperates with the
modular pinion gear housing subassembly 16; a rack (not shown)
cooperating with another portion of the modular pinion gear housing
subassembly 16; a pair of tie rods 18 cooperating with a and the
tires 20 which cooperate with tie rods 18. An electric motor 22 is
coupled to the modular pinion gear housing subassembly 16 and is
used to assist the assembly 10 in turning the vehicle 11.
FIGS. 3 and 4 show a perspective view and a cross-sectional view of
one embodiment of the modular pinion gear housing subassembly 16
according to the present invention, wherein the modular pinion gear
housing subassembly 16 has as its major components a torsion bar 24
contained within an input portion 26 of the pinion shaft 27, a
portion of an optical torque sensor 28 (fully shown in FIG. 5
below) having a lower sensor disk 30 and a upper sensor disk 32,
and a pinion gear 34. The lower sensor disk 32 has a first outer
diameter having a first bar code sequence thereon. The upper sensor
disk 32 has a second outer diameter having a second bar code
sequence thereon. When the steering wheel 12 turns, the torsion bar
24 twists in response to this turning. This causes relative
movement of the lower sensor disk 30 to the upper sensor disk 32,
and the optical pickup (not shown) of the sensor 28 picks up this
movement by reading sections of the bar codes in a method well
known in the art.
A torsion bar o-ring 40 seals the torsion bar 24 within the input
portion 26. A torque sensor support needle 42 is pressed on the
input portion 26. A gear 38 coupled from the electric motor 22 is
coupled to the output portion 44 of the pinion shaft 27. The gear
38 is preferably a hypoid shaped gear.
FIG. 6 shows the same cross-sectional view of the present invention
of FIG. 4, wherein the electric motor 22 and rack 36 are also shown
and the modular pinion gear housing assembly 16 is substantially
contained within a pinion housing 54. FIG. 2 shows the electric
motor 22 prior to assembly on the modular pinion gear housing
subassembly 16.
Referring now to FIGS. 4 and 5, the modular pinion gear housing
subassembly 16 is shown substantially within the pinion housing 54,
where the pinion gear 34 is coupled to the rack 36. FIGS. 4 and 5
also show the electric motor 22 coupled to and uncoupled from the
modular pinion gear subassembly.
The electric motor 22 is coupled to the subassembly 16 by pressing
the gear 38 onto the output portion 44. The pinion housing 54
contains a snap ring 52 installed thereon. The pinion housing 54
further contains an upper angular contact bearing 56, a sensor dust
seal 58, and a lower angular contact bearing 60. The upper angular
contact bearing 56 and the sensor dust seal 58 are pressed onto the
pinion housing 54. The lower angular contact bearing 60 is pressed
into a threaded housing 61. The angular contact bearings 56, 60
function to rotatably support the gear housing subassembly 16
within the pinion housing 54. The pinion housing 54 substantially
contains most of the modular pinion gear housing subassembly 16,
with a portion of input portion 26 and pinion gear 34 not contained
within the pinion housing 54.
To assemble the modular pinion gear housing subassembly 16
according to this preferred embodiment, each subassembly of the
modular pinion gear housing subassembly 16 must first be completed.
To assemble the pinion subassembly 90, first the gear 38 is pressed
onto the output portion 44. Next, the torsion bar 24 is pressed
into the output portion 44 and pinned to the input portion 26,
completing the pinion subassembly 90.
The optical torque sensor subassembly 92 is then assembled by first
installing the torsion bar o-ring 40. Second, the torque sensor
support needle bearing 42 is pressed into the input portion 26.
Third, the lower sensor disk 30 of the optical torque sensor 28 is
pressed onto the input portion 26 and the upper sensor disk 32 of
the optical torque sensor 28 is pressed onto the shoulder 46 of the
output portion 44. Fifth, the output portion 44 is slid over the
torsion bar 24 and into the input portion 26. Sixth, the output
portion 44 is drilled and pinned to the torsion bar 24. Finally, a
laser bar code is etched on the outer diameters of the lower sensor
disk 30 and the upper sensor disk 32 to complete the torque sensor
sub-assembly 92.
Next, the pinion housing subassembly 94 is assembled. First, a snap
ring 52 is installed on the pinion housing 54. Next, the upper
angular contact bearing 56 is pressed onto the pinion housing 54.
Finally, a sensor dust seal 58 is pressed into the pinion housing
54 to complete the pinion housing subassembly 94.
Pressing the lower angular contact bearing 60 into the threaded
housing 61 then completes the bearing housing subassembly 96.
The pinion subassembly 90 and torque sensor subassembly 92 is then
installed into the pinion housing subassembly 94, and the bearing
housing subassembly 96 in then installed into the pinion housing 54
and torqued to take out play in the angular contact bearings 56,
60. The modular pinion gear housing assembly 16 may then be bolted
onto a motor assembly (not shown) to complete torque sensor
evaluation and motor module evaluation prior to final gear
assembly. Having the capability of evaluating torque sensors and
motor modules prior to final assembly is of potentially great
advantage in that it may limit the time and cost necessary to
disassemble and replace non-working or out of specification
components.
In operation, an operator uses the steering wheel 12 to rotate the
steering shaft 14. The steering shaft 14 in turn twists the torsion
bar 24 and rotates the pinion gear 34. The pinion gear 34 in turn
acts on the rack 36, causing it to slide sideways within the gear
housing subassembly (not shown). As the rack 36 moves sideways, it
either pushes or pulls the tie rods 18, which in turn rotates the
steering knuckles (not shown) and front tires 20.
Also, when the steering wheel 12 is turned, the weight of the
vehicle 11 causes the front tires 20 to resist turning. This twists
the torsion bar 24, causing a relative angular displacement between
the lower sensor disk 30 and the upper sensor disk 32 of the
optical torque sensor 28, which exposes a different sequence of bar
codes on the outer diameters which are read by sensing equipment
(not shown) within the sensor 28. The sensing equipment is coupled
to a microprocessor based engine control module (not shown), which
is coupled to the electric motor 22. The engine control module
processes the sequence of bar codes and other vehicle parameters,
such as engine speed, to determine the proper amount of power
assist for the particular driving condition. The electronic control
module then sends a signal to instruct the electric motor 22 how
much assist to provide. Because the output portion 44 is connected
at one end to the torsion bar 24 and the input portion 26 to the
other, the assist torque delivered by the electric motor 22 to the
output portion 44 reduces the steering effort perceived by the
driver while exerting the necessary force on the rack 36 through
the coupled rack 36 and pinion gear 34 to steer the vehicle 11.
In another preferred embodiment of the present invention in
contrast to FIGS. 2-6 wherein one optical sensor 28 is used, a
plurality of optical torque sensors may be used to further verify
the change in bar code sequence. A plurality of optical sensors 28
provides a redundant system that is desirable in many automotive
applications. As illustrated, the torque sensors 28 are in separate
housings, however, they could also be contained within one
housing.
Referring now to FIG. 7, another embodiment of the modular pinion
gear housing subassembly 116 is disclosed coupled to the electric
motor 22 and the rack 136. In this embodiment, the optical torque
sensor 28 is replaced by a magnetoelectric sensor 168.
The modular pinion gear housing subassembly 116 has as its major
components pinion shaft 127 having an input portion 126, a
magnetoelectric sensor 168 containing torque-sensing coils 170, and
a pinion gear 134. A gear 138 from the electric motor 22 is coupled
to the pinion shaft 127. The gear 138 is preferably hypoid shaped.
It is contemplated that a torsion bar (not shown) may be added to
the subassembly 116 for damping or compliance reasons.
The modular pinion gear housing subassembly 116 is shown
substantially within the pinion housing 154, wherein the input
portion 126 and pinion gear 154 are not enclosed within the
housing. The assembly 116 in FIG. 7 is coupled to the electric
motor 22 and the rack 136. The pinion housing 154 contains a snap
ring 152 installed on the pinion housing 154. The pinion housing
further contains an upper angular contact bearing 156, a sensor
dust seal 158, and a lower angular contact bearing 160, all of
which are pressed onto the pinion housing 154. The angular contact
bearings 156, 160 function to rotatably support the gear housing
subassembly 116 within the pinion housing 154.
To assemble the modular pinion gear housing subassembly 116
according to this preferred embodiment, each subassembly of the
modular pinion gear housing subassembly 116 must first be
completed. To assemble the pinion shaft subassembly 190, first the
gear 138 is pressed onto the pinion shaft 126. Next, the
magnetoelectric sensor ring 162 is pressed onto the pinion shaft
126. Magnetic field conditioning is then performed, in which the
magnetoelectric sensor 168 is calibrated. Next, the snap ring 152
is installed to complete the pinion shaft subassembly.
Pressing the lower angular contact bearing 160 into the pinion
housing 154 then completes the pinion housing subassembly 192.
Next, the threaded housing subassembly is assembled by first
installing a snap ring 164 into a threaded housing 166 and then
pressing the upper angular contact bearing 156 into the threaded
housing 166. A donut-shaped magnetoelastic torque sensor 168
containing torque-sensing coils 170 is then pressed into the
threaded housing 166 to complete the threaded housing subassembly
194.
The pinion shaft subassembly 190 is then installed into the pinion
housing subassembly 192, followed by the threaded housing assembly
194, which is then torqued to take out play in the angular contact
bearings 156, 160. The completed modular pinion gear housing
subassembly 116 may then bolted onto a motor assembly (not shown)
to complete torque sensor evaluation and motor module evaluation
prior to final gear assembly. Having the capability of evaluating
torque sensors and motor modules prior to final assembly is of
potentially great advantage in that it may limit the time and cost
necessary to disassemble and replace non-working or out of
specification components.
In operation, an operator uses the steering wheel 12 to rotate the
steering shaft 14. The steering shaft acts on the pinion shaft 126,
which in turn rotates the pinion gear 134. The pinion gear 134 in
turn acts on the rack 136, causing it to move sideways within the
gear housing (not shown). As the rack 136 moves sideways, it either
pushes or pulls the tie rods 18, which in turn rotates the steering
knuckles (not shown) and front tires 20.
Also, when the steering wheel 12 is turned, the weight of the
vehicle 11 causes the front tires 20 to resist turning. This
strains the magnetoelastic material of the pinion shaft 126, which
causes the magnetic field to change within the threaded housing.
This change in magnetic field acts on the torque-sensing coils 170,
which are read by the sensing equipment (not shown) inside the
sensor 168. The sensing equipment is coupled to a microprocessor
based engine control module (not shown), which is coupled to the
electric motor 22. The engine control module processes the sequence
of magnetic changes and other vehicle parameters, such as engine
speed, to determine the proper amount of power assist for the
particular driving condition. The electronic control module then
sends a signal to instruct the electric motor 22 how much assist to
provide. Because the output portion 144 is connected at one end to
the torsion bar 124 and the input shaft 134 to the other, the
assist torque delivered by the electric motor 22 to the output port
ion 144 reduces the steering effort perceived by the driver while
exerting the necessary force on the rack 136 through the rack 136
and pinion gear 134 set to steer the vehicle 11.
While the invention has been described in terms of preferred
embodiments, it will be understood, of course, that the invention
is not limited thereto since modifications may be made by those
skilled in the art, particularly in light of the foregoing
teachings.
* * * * *